ABSTRACT Child care settings play a significant role in shaping the eating and physical activity habits of many young children. These programs can foster healthy behaviors by serving healthy foods and limiting access to unhealthy foods, integrating time for active play, limiting screen time, providing healthy role models, and teaching children the knowledge and skills needed to make healthy lifestyle choices. National efforts to address childhood obesity increasingly call upon child care programs to implement these evidence-based practices; however, compliance remains low. Implementation studies represent a critical next step in helping to advance child care-based health promotion and obesity prevention efforts. The proposed study (submitted in response to Dissemination and Implementation Research in Health, PAR-16-238), will address these gaps using a randomized controlled trial and hybrid effectiveness-implementation design to evaluate the impact of Go NAPSACC on centers' implementation of evidence-based practices and assess the reach, adoption, implementation, and maintenance that can be achieved with an Enhanced vs. Basic implementation model. We will target child care centers in Kentucky, the state with the sixth highest rate of child obesity in the U.S. We will work with The Kentucky Department of Health and eight of their existing regional technical assistance (TA) providers to recruit 97 child care centers (~12 centers per region). Regional TA providers delivering Enhanced Go NAPSACC will integrate steps from the Quality Implementation Framework to support general and intervention-specific capacity building by child care centers, which are hypothesized to improve the implementation of evidence-based best practices. Outcomes, guided by RE-AIM and Consolidated Framework for Implementation Research, will assess centers' implementation of evidence- based practices, changes in the diet quality and physical activity of children while at child care, markers of Go NAPSACC implementation, contextual factors influencing implementation, and costs.